Manufacture of alkyllead compounds with calcium-lead alloys



Patented 22, 1952 MANUFACTURE OF ALKYLLEAD COM- POUNDS WITH CALCIUM-LEAD ALLOYS livar T. Krohn, Royal Oak, and Hymin Shapiro, Detroit, Mich, assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware ,No Drawing. Application May 29, 1951, Serial No. 229,001

4 Claims.

This invention relates to a new process for making alkyllead compounds.

The most important of the alkyllead compounds is tetraethyllead which is made commercially by reacting monosodium-lead alloy with ethyl chloride in accordance with the following equation This process has been successful but it has certain disadvantages since three-fourths of the lead is not utilized in the reaction. The usual yield of tetraethyllead is only about 22 weight per cent based on the lead.

Among the objects of our invention is to provide a process in which the yield of tetraethyllead is higher than that obtained in the present process.

The above object is accomplished by reacting an alkylating agent with a particular calciumlead alloy composition. We have found that not all calcium alloys of lead are reactive. For instance, we have found that no alkyllead is formed from an alloy composition having an atom ratio of calcium to lead or 2 to l which corresponds to the formula CaaPb. This alloy is unreactive al though from a theoretical viewpoint it is the most desirable alloy since no free lead would be formed according to the reaction which may be expressed as follows:

in which R is an alkyl radical.

We have made the surprising discovery that high yields of alkyllead compounds based on the lead charged are made by an alloy in which the atomic ratio of calcium to lead is between about 1 to 1 and 1.5 to 1 and particularly with a composition consisting essentially of one atom of calcium for one atom of lead as expressed by the formula CaPb. The reaction between this alloy and an alkylating agent can be expressed as follows:

in which R is an alkyl radical and X is an inorganic acid radical which reacts with calcium to form a salt.

Any of the allrylating agents heretofore used or described in the prior art can be used, among which are the alltyl halides preferably the iodides, bromides and chlorides, the dialkyl sulfates and the trialkyl phosphates. In general, the alkylating agents are esters of inorganic acids having the proper alkyl groups for making the desired alkyllead compound, and having an inorganic acid group which forms a salt with calcium, Among those which can be used in our invention are the ethyl, propyl and butyl chlorides, as well a the corresponding bromides and iodides, diethylsulfate and triethylphosphate.

While tetraethyllead is the principal compound discussed herein because of its large commercial use, other alkyllead compounds such as tetramethyllead, tetrapropyllead, dimethyldiethyllead and methyltriethyllead can be made by the process of our invention.

The temperature employed is not important, thepreferablerange being 50 to 100 C. The pressure used is not critical but should be sufficient at the temperature employed to maintain the alkyl-- ating agent in the liquid phase. The time of reaction is between about 30 minutes and 8 hours. The amount of alkylating agent employed is not critical but an excess over the stoichiometric amount is preferred.

Our invention can be best understood by referring to the following typical working examples in which all the parts are by weight and the percentages are by weight based on the lead charged.

Example I A charge of 100 parts of calcium lead alloy having an atomic ratio of calcium to lead about 1 to 1 is added to the reaction vessel equipped with an agitator, a jacket for circulation of heating or cooling liquids, a reflux condenser, charging and discharging ports, liquid feed lines, and means for releasing the pressure. Liquid ethyl chloride in the amount of 209 parts is added under pressure to the stirred solids in the vessel over a period of one-half hour. By controlling the flow of liquid in the autoclave jacket and in the reflux condenser the temperature of the reaction mass is permitted to rise from an initial temperature of 50 C. to a temperature of C. during this feed period. The pressure in the autoclave during this feed rises to pounds per square inch gauge where it is maintained. The temperature of the stirred reaction mixture is maintained at 70 C. for about 5 hours at the end of which the pressure is reduced to atmospheric and the reaction mass removed and charged to a steam still wherein the alkyllead product is recovered. The yield of tetraethyllead is 52 parts or 40 per cent based on the lead present in the calcium lead alloy.

' Similarly when ethyl iodide or ethyl bromide are substituted in the above example, keeping all the conditions the same, substantially the 55 same yields are obtained, slightly higher yields being obtained with ethyl iodide. Also when the temperature of the reaction is raised to 85 C. substantially the same yield is obtained.

However, when the atomic ratio of calcium to lead was changed to about 2 to 1, which corresponds to the theoretical desirable composition of CazPb, no yield of tetraethyllead was obtained.

Thus, almost a two-fold yield over that obtained in the present commercial process is-made by our process in which the atomic ratio of calcium to lead is about 1 to 1.

In other examples when theatomic :ratio of calcium to lead was increasedtoaboutliiy-substantial yields of tetraethylleadwere-obtained;

Furthermore certain catalysts of-the carbonyl type substantially improves the results obtained. Among such catalysts are the ketones, aldehydes, acid anhydrides, esters and other derivatives of carboxylic acids.

Other embodimentsof our invention can be made without departing from the spirit and scope of ourinvention which isnot limited to specific embodiments given herein.

We claim:

1. The process for making Shydrocarbon-lead compounds "comprising reacting a calcium-lead alloy consisting" essentially of an alloy'having an atomic ratio of calcium to lead between about 1 to l and 1.5 to 1 with an alkylating agent which includes the hydrocarbon radical in question and having a negative radical which reacts with calcium.

3. The process of claim 1 for making tetrae-thyllead in which the alkylating agent is an ethylating agent.

4. The process of claim 1 for making tetraethyllead in which the alkylating agent is ethyl chloride.

IVAR T. KROHN. HYMIN SHAPIRO.

Hansen -Der 'Au'fbau der Zweistofilegieriengen, Edwards Bros. Inc., Ann Arbor, Michigan, 1943, pages 403-404.

Number 2 535,237

2. 'The process of claim'l'inwhich the atomic V ratio of calcium" to lead is about 1 to 1. 

1. THE PROCESS FOR MAKING HYDROCARBON-LEAD COMPOUNDS COMPRISING REACTING A CALCIUM-LEAD ALLOY CONSISTING ESSENTIALLY OF AN ALLOY HAVING AN ATOMIC RATIO OF CALCIUM TO LEAD BETWEEN ABOUT 1 TO 1 AND 1.5 TO 1 WITH AN ALKYLATING AGENT WHICH INCLUDES THE HYDROCARBON RADICAL IN QUESTION AND HAVING A NEGATIVE RADICAL WHICH REACTS WITH CALCIUM. 